Strategies for DNA sequencing may be grouped into several categories. (Shendure, J., et al., “Advanced sequencing technologies: methods and goals,” Nat. Rev. Genet., 5(5):335-44, 2004). They include (i) microelectrophoretic methods, (ii) sequencing by hybridization, (iii) real-time observation of single molecules, and (iv) cyclic-array sequencing. Available commercial products include 454 sequencing (used in the 454 Genome Sequencers, Roche Applied Science; Basel), Solexa technology (used in the Illumina (San Diego) Genome Analyzer), the SOLiD platform (Applied Biosystems; Foster City, Calif., USA), the Polonator (Dover/Harvard), and the HeliScope Single Molecule Sequencer technology (Helicos; Cambridge, Mass., USA).
One commonality of these sequencing techniques is the generation of a library from biological samples. Library preparation is accomplished by random fragmentation of DNA samples, followed by in vitro ligation of common adapter sequences. Further, what is common to these methods is that PCR amplicons derived from any given single fragmented DNA molecule in a library end up spatially clustered, either to a single location on a planar substrate (for example, in situ polonies, bridge PCR), or to the surface of micron-scale beads (for example, emulsion PCR).
New sequencing methods, commonly referred to as Next Generation Sequencing (NGS) technologies, may deliver fast, inexpensive and accurate genome information regarding biological samples through sequencing technologies. For example, high throughput NGS (HT-NGS) methods may allow scientists to obtain the desired sequencing information with greater speed, at lower cost and with acceptable error rate. One preliminary step for NGS is to prepare a nucleic acid library of the biological sample in such a way that is amenable to NGS technologies, for example, a library of short sequences with barcodes. Thus, there is a need to find new methods to construct barcoded library for sequencing purposes.